Your chest is the part of your body from your stomach to your neck. A bodybuilder or weightlifter is distinctive not only for his huge arms, but for his big, muscular chest.
The character Tarzan is known for thumping his own chest while yelling — but if Tarzan gets a bad cold, he might cough so hard that his chest aches. Another kind of chest is a storage box with a connected lid that swings open. This is the oldest meaning of chest, from the Old English cest, "box or casket." The anatomical meaning comes from the idea that the ribs form a "box" — or a chest — around the internal organs.